全文获取类型
收费全文 | 2383篇 |
免费 | 68篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 21篇 |
综合类 | 5篇 |
化学工业 | 954篇 |
金属工艺 | 39篇 |
机械仪表 | 41篇 |
建筑科学 | 197篇 |
矿业工程 | 7篇 |
能源动力 | 67篇 |
轻工业 | 198篇 |
水利工程 | 13篇 |
石油天然气 | 2篇 |
武器工业 | 4篇 |
无线电 | 123篇 |
一般工业技术 | 326篇 |
冶金工业 | 125篇 |
原子能技术 | 32篇 |
自动化技术 | 299篇 |
出版年
2022年 | 22篇 |
2021年 | 52篇 |
2020年 | 29篇 |
2019年 | 28篇 |
2018年 | 36篇 |
2017年 | 26篇 |
2016年 | 63篇 |
2015年 | 56篇 |
2014年 | 54篇 |
2013年 | 105篇 |
2012年 | 90篇 |
2011年 | 121篇 |
2010年 | 99篇 |
2009年 | 103篇 |
2008年 | 96篇 |
2007年 | 84篇 |
2006年 | 90篇 |
2005年 | 80篇 |
2004年 | 66篇 |
2003年 | 45篇 |
2002年 | 52篇 |
2001年 | 44篇 |
2000年 | 53篇 |
1999年 | 64篇 |
1998年 | 53篇 |
1997年 | 59篇 |
1996年 | 52篇 |
1995年 | 53篇 |
1994年 | 43篇 |
1993年 | 29篇 |
1992年 | 40篇 |
1991年 | 41篇 |
1990年 | 34篇 |
1989年 | 40篇 |
1988年 | 26篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 23篇 |
1984年 | 30篇 |
1983年 | 27篇 |
1982年 | 17篇 |
1981年 | 29篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 19篇 |
1977年 | 22篇 |
1976年 | 19篇 |
1975年 | 18篇 |
1974年 | 21篇 |
1973年 | 19篇 |
排序方式: 共有2453条查询结果,搜索用时 0 毫秒
21.
Matthias Berger Kurt Laumen Manfred P. Schneider 《Journal of the American Oil Chemists' Society》1992,69(10):955-960
Regioisomerically pure 1,3-sn-diacylglycerols are conveniently prepared in high yields (>80%) and in large quantities by enzymatic esterification of glycerol
in the presence of various 1,3-selective lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) and a variety of different acyl donors like free fatty acids, fatty acid alkyl esters and vinyl esters. All reactions are
carried out in aprotic organic solvents of low water content, namelyn-hexane, diethyl ether or tBuOMe. The creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol
and the hydrophobic reaction media by the adsorption of glycerol onto a solid support prior to use was essential for the success
of these transformations. The effects of reaction conditions and the regioselectivities of the lipases on the product yields
are described in detail. 相似文献
22.
Statistical Analysis of the Intergranular Film Thickness in Silicon Nitride Ceramics 总被引:1,自引:0,他引:1
Hans-Joachim Kleebe Michael K. Cinibulk Rowland M. Cannon Manfred Rüble 《Journal of the American Ceramic Society》1993,76(8):1969-1977
Silicon nitride materials typically reveal thin amorphous intergranular films along grain boundaries, with only the exception of special boundaries. It is known that such grainboundary films strongly affect the high-temperature properties of the bulk material. High-resolution electron microscopy (HREM) was used to study these amorphous films in different Si3 N4 ceramics. The observed film thicknesses at grain boundaries in these materials varied between 5and 15 Å. It was shown that the grain-boundary film thickness strongly depends on film chemistry. Careful inspections of film-thickness measurements across grain boundaries in a given material suggest that the film widths vary on the order of 1 Å. Therefore, a quantitative evaluation should allow for the determination of the standard deviation of the film thickness. The amorphous film widths along grain boundaries in four materials were measured over the entire length (up to 1 μm) of the grain boundary between two triple points. Forty to fifty data points were evaluated for each boundary, giving a Gaussian-like distribution of the film thickness around a median value, which corresponded well with the film width measured from single HREM micrographs. The accuracy achieved by the statistical method was better than ± 1 Å. 相似文献
23.
24.
Corrosion of oil-fired domestic boilers Depending on the surface temperature of the flue gas side the corrosion of oil fired domestic boilers proceeds either mainly by acid corrosion or by oxygen corrosion:
- – At surface temperatures of 60°C and higher the corrosion mechanism of acid corrosion prevails and the corrosion rates amount to 0.1–0.3 mm/year (values referred to continuous burner operation). The corrosion products consist of soluble iron(II)- and iron(III)sulfates. Higher corrosion rates can be attributed to an appreciable catalytic formation of sulfur trioxide on the corrosion products formed on the convective heating surfaces.
- – At surface temperatures of 40°C the mechanism of oxygen corrosion already dominates and the corrosion rates are about ten times higher (1.5–3 mm/year, referred to continous burner operation). The high portion of ioron oxide hydrates, especially goethit (α-FeOOH), makes the corrosion products difficult to remove.
- – Distinctly reduced service lives are also expected for the so called reduced temperature boilers (“Niedertemperaturkessel”) and low temperature boiers (“Tieftemperaturkessel”): According to the manufacturers these boilers may be operated at boiler water temperatures well below 60°C, as they are equipped with constructive measures to enhance the surface temperature on the flue gas side. However, these measures are only fully effective under stationary conditions.
25.
Ines Hofinger Jörg Möller Manfred Bobeth Karen Raab 《Journal of Thermal Spray Technology》2002,11(3):387-392
The adherence of plasma sprayed NiCrAlY bond coats can be improved by an appropriate substrate surface finish. The interface
fracture energy for crack propagation along the coating/substrate interface has been measured for different surface roughness
by means of a specially designed four-point bending test. An increase of the interface fracture energy of about 15% was observed
for a three times higher surface roughness. In addition, four-point bending tests with the coating on the side face of bending
specimens were performed to analyze the fracture and spalling behavior of the coatings both under large tensile and compressive
substrate deformations. 相似文献
26.
Topology optimization of a cantilevered piezoelectric energy harvester using stress norm constraints
Fabian Wein Manfred Kaltenbacher Michael Stingl 《Structural and Multidisciplinary Optimization》2013,48(1):173-185
Vibrational piezoelectric energy harvesters are devices which convert ambient vibrational energy into electric energy. Here we focus on the common cantilever type in which an elastic beam is sandwiched between two piezoelectric plates. In order to maximize the electric power for a given sinusoidal vibrational excitation, we perform topology optimization of the elastic beam and tip mass by means of the SIMP approach, leaving the piezoelectric plates solid. We are interested in the first and especially second resonance mode. Homogenizing the piezoelectric strain distribution is a common indirect approach increasing the electric performance. The large design space of the topology optimization approach and the linear physical model also allows the maximization of electric performance by maximizing peak bending, resulting in practically infeasible designs. To avoid such problems, we formulate dynamic piezoelectric stress constraints. The obtained result is based on a mechanism which differs significantly from the common designs reported in literature. 相似文献
27.
Jolita Ralyt Manfred A. Jeusfeld Per Backlund Harald Kühn Nicolas Arni-Bloch 《Information Systems》2008,33(7-8):754
Interoperability is a key property of enterprise applications, which is hard to achieve due to the large number of interoperating components and semantic heterogeneity. The inherent complexity of interoperability problems implies that there exists no silver bullet to solve them. Rather, the knowledge about how to solve wicked interoperability problems is hidden in the application cases that expose those problems. The paper addresses the question of how to organise and use method knowledge to resolve interoperability problems. We propose the structure of a knowledge-based system that can deliver situation-specific solutions, called method chunks. Situational Method Engineering promotes modularisation and formalisation of method knowledge in the form of reusable method chunks, which can be combined to compose a situation-specific method. The method chunks are stored in a method chunk repository. In order to cater for management and retrieval, we introduce an Interoperability Classification Framework, which is used to classify and tag method chunks and to assess the project situation in which they are to be used. The classification framework incorporates technical as well as business and organisational aspects of interoperability. This is an important feature as interoperability problems typically are multifaceted spanning multiple aspects. We have applied the approach to analyse an industry case from the insurance sector to identify and classify a set of method chunks. 相似文献
28.
Scherer HU Wang J Toes RE van der Woude D Koeleman CA de Boer AR Huizinga TW Deelder AM Wuhrer M 《Proteomics. Clinical applications》2009,3(1):106-115
In several autoimmune disorders, including rheumatoid arthritis (RA), autoantibodies are thought to be the driving force of pathogenicity. Glycosylation of the Fc-part of human Igs is known to modulate biological activity. Hitherto, glycosylation of human IgG-Fc has been analyzed predominantly at the level of total serum IgG, revealing reduced galactosylation in RA. Given the pathogenic relevance of autoantibodies in RA, we wished, in the present study, to address the question whether distinct Fc-glycosylation features are observable at the level of antigen-specific IgG subpopulations. For this purpose, we have developed a method for the microscale purification and Fc-glycosylation analysis of anti-citrullinated peptide antibodies (ACPA). ACPA represent a group of autoantibodies that occur with unique specificity in RA patients. Their presence is associated with increased inflammatory disease activity and rapid joint destruction. Results indicate that ACPA of the IgG1 subclass vary considerably from total serum IgG1 with respect to Fc-galactosylation, with galactosylation being higher on ACPA than on serum IgG1 for some patients, while other patients show higher galactosylation on serum IgG1 than on ACPA. Using this method, studies can be performed on the biological and clinical relevance of ACPA glycosylation within RA patient cohorts. 相似文献
29.
30.
Daniele Colombo Slah Drira Ralf Frotscher Manfred Staat 《International journal for numerical methods in engineering》2023,124(2):402-433
Edge-based and face-based smoothed finite element methods (ES-FEM and FS-FEM, respectively) are modified versions of the finite element method allowing to achieve more accurate results and to reduce sensitivity to mesh distortion, at least for linear elements. These properties make the two methods very attractive. However, their implementation in a standard finite element code is nontrivial because it requires heavy and extensive modifications to the code architecture. In this article, we present an element-based formulation of ES-FEM and FS-FEM methods allowing to implement the two methods in a standard finite element code with no modifications to its architecture. Moreover, the element-based formulation permits to easily manage any type of element, especially in 3D models where, to the best of the authors' knowledge, only tetrahedral elements are used in FS-FEM applications found in the literature. Shape functions for non-simplex 3D elements are proposed in order to apply FS-FEM to any standard finite element. 相似文献